Gene therapy is the use of DNA as a drug or a pharmaceutical agent to treat disease by delivering therapeutic DNA into a patient's cells. The technique emphasizes that DNA can be used to supplement or alter genes within an individual's cells as a therapy to treat disease. The most common form of gene therapy involves using DNA that encodes a functional, therapeutic gene to replace a mutated gene.
There are many methods adopted to try and correct the altered genes:
1. A normal gene can be inserted into a non-specific location within the genome to replace a non-functional gene.
2. An abnormal gene could be swapped for a normal gene through homologous recombination.
3. The abnormal gene could be repaired through selective reverse mutation, which returns the gene to its normal function.
4. The regulation (act of turning the gene on or off) of a particular gene could be altered.
DNA that encodes a therapeutic protein is packaged within a "vector", which is used to get the DNA inside cells within the body. Once inside, the DNA gets expressed by the cell machinery, resulting in the production of therapeutic protein, which in turn treats the patient's disease.